htop uses a sophisticated color-coding system to represent system resource utilization at a glance. The default color scheme breaks down as follows:

Green: 0-60% utilization (normal operation)
Blue:  60-80% (moderate load)
Yellow: 80-90% (high load)
Red:   90-100% (critical)

When memory shows minimal green/blue and predominantly yellow (as in your screenshot), this indicates:

• ~10-20% of RAM is in normal usage (green/blue)
• 80-90% of RAM is actively utilized (yellow)
• Swap remains unused (ideal situation)

You can modify these thresholds in ~/.config/htop/htoprc:

# CPU threshold percentages
cpu_count=4
cpu_green=60
cpu_blue=80
cpu_yellow=90

# Memory thresholds
mem_green=50
mem_blue=70
mem_yellow=85

For a system showing your pattern (high yellow memory), consider these actions:

# Identify memory-hungry processes
ps -eo pid,ppid,cmd,%mem,%cpu --sort=-%mem | head

# Clear page cache (temporary relief)
echo 1 > /proc/sys/vm/drop_caches

Combine htop visualization with precise metrics:

# Live memory breakdown
watch -n 1 "free -h && echo '' && vmstat -s"

When working with htop, the color-coded bars provide crucial visual indicators about system resource utilization. The default color scheme follows this pattern:

• Green: Represents memory used by processes
• Blue: Shows buffer/cache memory
• Yellow: Indicates memory that's been allocated but not actively used
• Red: Signals swap space usage

The scenario you described - with small green/blue segments and mostly yellow - reveals:

Memory breakdown:
- Active processes (green): Minimal
- Buffers/cache (blue): Small amount
- Inactive memory (yellow): Dominant portion
- Swap (red): Unused (empty bar)

This typically indicates a system where:

1. Few active processes are consuming RAM
2. The kernel has allocated memory that isn't currently being utilized
3. No memory pressure exists (hence no swap usage)

You can modify these thresholds in ~/.config/htop/htoprc:

# Sample configuration for memory meter colors
color_mem_buffer=38;5;27
color_mem_cache=38;5;39
color_mem_used=46
color_mem_free=148

Here's a bash snippet to log memory patterns similar to htop's display:

#!/bin/bash
while true; do
    free -m | awk '/Mem:/ {
        printf "Memory: %.1f%% active (green), %.1f%% buffers (blue), %.1f%% inactive (yellow)\n",
        $3/$2*100, $6/$2*100, ($5-$6)/$2*100
    }'
    sleep 5
done

While yellow memory isn't inherently problematic, watch for these patterns:

For developers optimizing memory usage, consider:

# Check detailed slab info (requires root)
sudo cat /proc/meminfo | grep -E 'Active|Inactive|Slab'

This helps distinguish between:

• Active memory (green)
• Reclaimable cache (blue)
• True inactive memory (yellow)